It has been noted for some time that in the combination of extremely high speeds and watercraft, there is a high degree of uncertainty and difficulty in predicting performance and behaviour. Most manufacturers use their experience gained from more of a trial-and-error approach as the key to the performance they have derived. In aerospace, for example, far more computational analysis is conducted on every design detail before committing to manufacturing.
Structural analysis (FEA) has been increasingly used to optimize metallic & composite structures. Still, the inherent problem is always which load cases are applied, and the difficulties in measuring accurately the surface pressures and forces that hulls encounter in seas at higher speeds. Traditional studies on test hulls using pressure gauges have been conducted. Still, the conclusion has mostly been that the pressure variation is so highly concentrated and distributed, that a true insight into what is going on is challenging to gleam.
When it comes to analyzing a hull, it is extremely difficult to know what pressure distribution to apply in simulations to properly analyze hull slamming (typically the peak loadcase on a high speed boat).
Current industry practice
The current CFD tools are focused on what can be simulated, especially when simultaneously examining multiple aspects. This is satisfactory for examining the aerodynamics on its own or for running a hydrodynamic analysis, but it is fraught with danger and erratic results, especially at high speed. Running an accurate multiphase fluid analysis has been the holy grail for designers to properly simulate, understand, and optimize a hull.
However, the limitations of existing software and CFD codes, the lack of people able to conduct this analysis, and the computing requirements needed to deliver decent resolution have been barriers to using these tools for the general marine industry, especially the high-speed sector.
CMN NAVAL approach
The Group has materialized a series of programs with CFD companies (both consultants and software companies) to try to understand the root of this problem. However, none could provide a suitable answer, so the only option was to use the tools on single-phase flow in isolation, optimize from there, and combine the results manually into the calculations.
Around spring last year, CMN NAVAL contacted an aerodynamics team grouped in academia (fresh off the back of designing of a high profile land speed record project). In addition to this team, the Group recruited Formula 1 aerodynamics experts to consult on a number of projects, in order to bring in a type of thinking not usually met in the marine industry.
Results
The results of the collaboration (which is on-going), are two-fold:
Bespoke CFD software has been created specifically and exclusively to resolve the abovementioned problems. Furthermore, the inclusion of some state-of-the-art AI (Artificial Intelligence) features, more commonly found in automotive and aerospace industries, has been completed.
A high-speed vessel is being designed using all these techniques and methods, combining the experience of the design team and consultants.
At present, the hull and deck geometries can be optimized to generate 60% more lift and less drag than the conventional high-performance baseline design, and significant further gains are still being found.
